Teenagers have picked up a worrying habit, and no one noticed for years

Every two years years, the government releases a report on the state of the American teenager. And the most recent, released last Friday and using data from 2015, offers mostly good news. From sea to shining sea, American adolescents are having smarter sex, doing drugs less, and almost always using seat belts.

So they're a bunch of brown-nosing goody-two-shoes, basically.

However, there was one major spot of bad news in the report: The youths are vaping like crazy.

A full 44.9% of teens reported using electronic cigarettes ever, and 24.1% had done so in the last month. That's nuts — compare that stat to the 30.1% who had sex in the three months before the survey, 22.6% who had ever been in a fight, or 6.1% who drove without seatbelts. What's up Gen-Z? You were holding it together so well. And then came the nasty vapor clouds.

Nicotine in e-cigs is addictive, just like it is in analog cigarettes.

Teens who smoke e-cigs are also more likely to smoke regular cigarettes, according to a recent study, though scientists have not established a causal link between the two habits.

Those other substances in e-cig cartridges range from "probably harmless" to " definitely bad for you" (more research is needed), and the ratio of one to the other can vary significantly from a local mom-and-pop vape shop to a big, professional purveyor.

Because of that inconsistency, among other reasons, there's little data on exactly how bad e-cigs are for you.

However, if millions of teens are encountering nicotine for the first time in e-cigarettes, rather than using e-cigarettes to wean themselves off tobacco, that's bad news for the pro-vape argument — and probably for those teens, too.